Winding having a two turn conductive strip therearound



July 23, 1968 R, w, AIKEN (ET AL 3,394,331

WINDING HAVING A TWO TURN CONDUCTIVE STRIP THEREAROUND Filed June :1,1966 United States Patent 3,394,331 WINDING HAVING A TWO TURN CONDUCTIVESTRIP THEREAROUND Robert W. Aiken and Robert E. Canup, Richmond, Va.,

assignors, by mesne assignments, to Texaco, Inc., New

York, N.Y.

Filed June 2, 1966, Ser. No. 554,785 3 Claims. (Cl. 336-70) ABSTRACT OFTHE DISCLOSURE High voltage coil structure for a transformer or thelike. Individual turns of winding layers are spaced apart and theoutermost two winding layers are strips that extend the full width ofthe next outermost layer of winding turns.

BACKGROUND OF THE INVENTION It has been recognized in high voltageinduction equipment, especially transformers and the like, that there isinsulation difiiculty with respect to the outer layers or windings ofinduction coils. Such difliculty stems from the tendency forconcentration of voltage especially where a transient or rapidlychanging voltage is applied. The concentration arises in the outermostlayers of a high voltage winding so that the insulation tends to breakdown and cause short circuiting between turns of the coil. An obvioussolution that has been applied is increased insulation thickness, and/oradded spacing between turns of the coil on the outer layers. However, ithas long been recognized that such solution entails suflicient addedbulk and expense so as to leave much to be desired.

Some previous solutions have included the use of shielding layers suchas to provide capacitive effects and thus avoid the excess high tensionconditions. However, such attempts have been applied only to large sizepower transformers and the like; and .on account of the complications inmanufacture and the bulk of the structure involved such structure is notapplicable to a relatively small sized transformer such as the typeemployed with an internal combustion engine ignition system.

In addition, the known previous structures that provide shieldingagainst high tension concentration effects have employed structure suchthat the shielding layers are applied in an electrically floating mannerwhich fails to obtain the dual function quality that is obtained withstructure according to this invention.

DESCRIPTION OF THE INVENTION It is an object of this invention toprovide improved winding structure for a high voltage coil such that theoutermost turns of the coil take the form of a conductive material stripthat is at least as wide as the length of the coil winding layerthereunder.

Briefly, the invention concerns high voltage induction machinery.Specifically it deals with the combination of an improved high voltagecoil that comprises a plurality of winding layers having predeterminedaxial dimensions. And it comprises at least .one turn of a conductingmaterial strip that surrounds the outermost of said winding layers. Thesaid strip covers said winding layers and forms a corona shieldtherefor.

The foregoing and other objects and benefits of the invention will bedescribed in greater detail hereafter in accordance with the best modecontemplated for carrying out the invention, and in connection withwhich there are the illustrations of the drawings, wherein:

The figure of drawing shows a schematic elevation partly incross-section, illustrating a high voltage winding 3,394,331 PatentedJuly 23, 1968 for a transformer or the like, in accordance with theinvention.

A preferred embodiment according to this invention relates to the highvoltage coil of transformers. The transformer being one especiallyintended for use in internal combustion engine ignition systems.

Referring to the figure of drawing, it will be observed that there is acore element 11. This may take various forms, but as schematicallyindicated by the dashed lines it could be a closed rectangular shape. Insuch cases the primary winding or low voltage winding (not shown) of thetransformer would be located on another leg (not shown) of the coreparallel to that illustrated.

Core member 11 is preferably constructed of magnetically permeablematerial, such as soft iron or the like, and as indicated in thedrawings is preferably laminated in order to reduce eddy currentelfects, as is standard practice for core materials. Surrounding thecore 11 there is a coil form 12 that is constructed of insulatingmaterial.

As schematically indicated, the total coil of the illustratedtransformer is made up by winding a conducting material wire 15 aroundthe coil form 12 so as to form a plurality of layers 16-20 illustrated.It will be observed that these winding layers 16-20 are tapered in axiallength as they progress outward from the coil form 12. This is done inorder to provide a decrease in voltage per layer as the layers progressoutwardly toward the outside of the coil. The individual turns of thewinding layers are separated by two diameter spacing (center to center)of the wire 15 as the turns are laid on. Each layer of turns isseparated from the next successive layer by a thin sheet of insulatingmaterial 23. This is preferably a material such as that known by thetrade name Mylar.

Outside of the last layer of turns 20 there is a double thickness sheetof insulating material 24, and on top of sheet 24 there is a completefirst turn of a conducting material strip 25. Strip 25 is wrapped fortwo turns so that there is another layer of the insulating materialsheet 26 that separates the first turn from the second or outermostturn.

It will be observed that the two turns of strip 25 are electricallyconnected in series with the coils (wrapped in layers 1620) so as toform the last two turns of the total coil. This is accomplished in anyfeasible manner such as by carrying the end .of the last turn on outerlayer 20 around one edge of the strip or sheet 24, as illustrated, by ashort connecting wire 30. The outermost or free end of strip 25 is thenconnected to a terminal wire 31. The other end of the complete coil isbrought out from the coil structure via a terminal wire or connecter 32,as illustrated.

The outermost or covering layer for the coil is preferably a triplethickness sheet 35. This is preferably constructed of the sameinsulating material as that employed in the inner separating sheets 23and 24 and 26.

It will be observed that by use of the illustrated structure for a highvoltage inductive coil, substantially higher voltage may be appliedwithout damage to the coil than was heretofore possible, in the absenceof known techniques such as increasing insulation on the outer layers bylarge increases in thickness and/or very wide spacing and the like.Consequently, the high voltage results obtained are obtainable withcompact and inexpensive structure so that a transformer using thestructure of this invention is applicable to extra high voltage internalcombustion engine ignition systems.

It will be noted also that with structure according to this inventioneven in the event that corona discharge should cause deterioration ofthe insulation to the point where it becomes punctured, there isinsuflicient voltage between layers (since the outer two layers consistof a single turn each) to cause arc-over and perforce shorting betweenlayers or turns.

While a particular embodiment'of the invention has been described abovein considerable detail in accordance with the applicable statutes, thisis not to be taken as in any way limiting the invention but merely asbeing descriptive thereof.

We claim:

1. In high voltage induction machinery, in combination an improved highvoltage coil comprising a plurality of winding layers havingpredetermined axial dimensions,

said winding layers being tapered in axial length thereof as theyprogress outward from the axis of the coil in order to reduce thevoltage per layer, and a conducting material winding comprising a stripsurrounding the outermost of said winding layers,

said conducting material winding strip having at least two turns andbeing connected in series with the end of said outermost winding layer,

said strip covering said winding layers and forming a corona shieldtherefor.

2. A high voltage coil according to claim 1 wherein the turns of saidwinding layers are spaced mutually apart by a distance of two diameterscenter to center.

3. A high voltage coil according to claim 2 wherein said strip is widerthan the axial dimension of said outermost layer, and

further including a terminal connection electrically connected to theoutermost end of said strip.

References Cited LARAMIE E. ASKIN, Primary Examiner.

T. J. KOZMA, Assistawt Examiner.

